A peat substrate is made from peat from drained peatlands, which is a limited resource. A realistic estimate is that 50% of the world’s wetlands have been lost. Peat is used in horticulture, especially for the cultivation of vegetables in greenhouses. The consequences of peatland exploitation are an increase in the greenhouse effect and a decrease in carbon stocks. Wood fiber can be used as an alternative to peat. The chemical properties of growing media interact and change continuously due to the small volume of growing media, which is limited by the growing container. This study aims to gain new knowledge on the impact of nutrient changes in the microbial degradation of carbon compounds in wood fiber and mixtures with a peat substrate on the content and uptake of nutrients required by plants. The cucumber (Cucumis sativus L.) variety ‘Dirigent H’ developed in the Netherlands was cultivated in growing media of a peat substrate and wood fiber: (1) peat substrate (PS); (2) wood fiber (WF); (3) wood fiber and peat substrate 50/50 v/v (WF/PS 50/50); (4) wood fiber and peat substrate 25/75 v/v (WF/PS 25/75). The rates of fertilization were the following: (1) conventional fertilization (CF); (2) 13 g N per plant (N₁₃); (3) 23 g N per plant (N₂₃); (4) 30 g N per plant (N₃₀). The experiment was carried out with three replications. As the amount of wood fiber increased, the humidity and pH of the growing media increased. The fertilization of the cucumbers with different quantities of nitrogen influenced the nutrient uptake. The plants grown in the 50/50 and 25/75 growing media had the best Cu uptake when fertilized with N₂₃. When the plants grown in the wood fiber media and the 50/50 media were fertilized with N₁₃, N_23, and N₃₀, the Mn content in the growing media at the end of the growing season was significantly lower than the Mn content in the media with conventional fertilization. Thus, nitrogen improved the uptake of Mn by the plants grown not only in the wood fiber, but also in the combinations with a peat substrate. Growing plants in wood fiber and fertilizing them with N₁₃ can result in the optimum uptake of micronutrients. The number and biomass of cucumber fruits per plant were influenced by the amount of wood fiber in the growing media and the application of nitrogen fertilizer. The highest number of fruits and biomass of fruits per plant obtained were significantly higher when the cucumbers were grown in WF/PS 50/50 growing media with additional N₁₃ fertilization.

As the consumption of plant products grown under regulated-climate conditions intensifies, its production also intensifies. Peat substrate as a growing medium is widely used due to its desirable physical, chemical, and biological properties. Peatlands play an important ecological, economic, and cultural role in human well-being, but their resources are decreasing, so wood fiber can be used as a substitute for peat substrate. Cucumbers (Cucumis sativus L.) were cultivated in growing media (Factor A) of peat substrate and wood fiber: (1) peat substrate (PS); (2) wood fiber (WF); (3) WF and PS 50:50 v/v; or (4) WF and PS 25:75 v/v. To evaluate the amount of additional nitrogen, four fertilization rates were used (Factor B): (1) conventional fertilization (CF); (2) N₁₃; (3) N₂₃; or (4) N₃₀. The yield of cucumbers grown in wood fiber depended on the amount of additional nitrogen. When plants were fertilized with the highest rate of additional nitrogen, N₃₀, their yield increased by 22% compared to the yield of cucumbers that were grown in wood fiber using conventional fertilization. Chlorophyll synthesis was the most intense in the leaves of cucumbers grown in wood fiber when the plants were additionally fertilized with N₂₃ and N_30, and in mixtures of wood fiber with peat substrate in ratios of 50:50 and 25:75, fertilized with N₂₃ and N₁₃, respectively. In summary, it can be argued that cucumbers can be grown in wood fiber and in a mixture with peat substrate in a ratio of 50:50, but additional nitrogen is needed to compensate for the amount of nitrogen immobilized in the fiber.

: Greenhouse plants are usually grown in containers filled with growing media. Peat is the main component of the growing media used in greenhouses. However, peat substrate is made from peat from drained peatlands, which is a limited resource. Wood fiber can be an alternative to use as a growing media for controlled-climate crops. The chemical properties of the growing media interact and change continuously due to the small volume of the growing media, which is limited by the vegetative container. Therefore, this study aims to gain new knowledge on the impact of nutrient changes in the microbial degradation of carbon compounds in wood fiber and mixtures with peat substrate on the content and uptake of nutrients required by plants. Cucumbers (Cucumis sativus L.) were cultivated in growing media of peat substrate and wood fiber: (1) peat substrate (PS); (2) wood fiber (WF); (3) wood fiber and peat substrate 50/50 v/v (WF/PS 50/50); (4) wood fiber and peat substrate 25/75 v/v (WF/PS 25/75). The rates of fertilization were the following: (1) conventional fertilization (CF); (2) N13; (3) N23; (4) N30. Fertilization of cucumbers with different rates of nitrogen influenced the nutrient uptake. Plants grown in WF/PS 50/50 and WF/PS 25/75 growing media had the best Cu uptake when fertilized with N23. When the plants grown in the wood fiber media and the 50/50 media were fertilized with N13, N23, and N30, the Mn content in the growing media at the end of the growing season was significantly lower than the Mn content in the media with conventional fertilization. Thus, nitrogen improved the uptake of Mn by plants grown not only in the wood fiber but also in combinations with peat substrate. Growing plants in wood fiber and fertilizing them with N13 can result in optimum uptake of micronutrients. The number and mass of cucumber fruits per plant were influenced by the amount of wood fiber in the growing media and the application of nitrogen fertilizer. The highest number of fruits and mass of fruits per plant was obtained significantly higher when cucumbers were grown on WF/PS 50/50 growing media with additional N13 fertilization.

A field experiment was carried out at the Experimental Station of the Aleksandras Stulginskis University in 2011 with the objective to establish the influence of spring oilseed rape (Brassica napus L.) crop density (50–100, 100–150, 150–200, 200–250, 250–300, 300–350, 350–400, 400–450 plants m^–2) on plant root biomass and soil enzymes urease and saccharase activity. It was found that the highest plant root biomass in the 0–10 and 10–20 cm soil layers was formed at a plant density of 100–150 plants m^–2. With rape crop density increasing from 150 to 450 plants m^–2, a decreasing trend of plant root biomass in both soil layers was detected. Statistically significant dependencies were determined between the dry biomass of oilseed rape roots in the 0–10 cm soil layer and the content of potassium in the soil (r = 0.76, P < 0.05), and between the dry biomass of rape roots in the 10–20 cm soil layer and soil pH (r = 0.74, P < 0.05). With increasing rape crop density, compared with the thinnest crop, the activity of urease in the soil did not change significantly. At a rape crop density of more than 100 plants m^–2 the activity of saccharase significantly increased (by 31–56%) in comparison with saccharase activity in the thinnest crop. The soil urease activity depended on the spring rape crop density (r = 0.81, P < 0.05) and the content of available phosphorus (r = 0.75, P < 0.05). The soil saccharase activity was influenced by the rape crop density (r = 0.79, P < 0.05) and soil pH (r = 0.72, P < 0.05).

Plant fertility and soil quality are determined by many environmental factors

:Peat substrate is made from peat from drained peatlands, which is a limited resource. A realistic estimate is that 50% of the world’s wetlands have been lost. Peat is used in horticulture, especially for the cultivation of vegetables in greenhouses. The consequences of peatland exploitation are an in-crease in the greenhouse effect and a decrease in carbon stocks. Wood fiber can be used as an al-ternative to peat. The chemical properties of the growing media interact and change continuously due to the small volume of the growing media, which is limited by the growing container. This study aims to gain new knowledge on the impact of nutrient changes in the microbial degradation of carbon compounds in wood fiber and mixtures with peat substrate on the content and uptake of nutrients required by plants. Cucumbers (Cucumis sativus L.) variety “Dirigent H” developed in the Netherlands, were cultivated in growing media of peat substrate and wood fiber: (1) peat substrate (PS); (2) wood fiber (WF); (3) wood fiber and peat substrate 50/50 v/v (WF/PS 50/50); (4) wood fiber and peat substrate 25/75 v/v (WF/PS 25/75). The rates of fertilization were the following: (1) con-ventional fertilization (CF); (2) N13; (3) N23; (4) N30. The experiment was carried out in three repli-cations. As the amount of wood fiber increased, the humidity and pH of the growing medium in-creased. Fertilization of cucumbers with different rates of nitrogen influenced the nutrient uptake. Plants grown in 50/50 and 25/75 growing media had the best Cu uptake when fertilized with N23. When the plants grown in the wood fiber media and the 50/50 media were fertilized with N13, N23, and N30, the Mn content in the growing media at the end of the growing season was significantly lower than the Mn content in the media with conventional fertilization. Thus, nitrogen improved the uptake of Mn by plants grown not only in the wood fiber but also in combinations with peat sub-strate. Growing plants in wood fiber and fertilizing them with N13 can result in optimum uptake of micronutrients. The number and mass of cucumber fruits per plant were influenced by the amount of wood fiber in the growing media and the application of nitrogen fertilizer. The highest number of fruits and mass of fruits per plant was obtained significantly higher when cucumbers were grown on WF/PS 50/50 growing media with additional N13 fertilization.